Re: Trying to understand the 453 calibrator


Harvey White
 

The calibrator square wave is intended to be a voltage reference and not a time reference, not in the early scopes.  For a scope with a microprocessor in it, it can be derived from the processor clock, for a scope with lots of digital electronics, generally from a master oscillator.  In addition, it's used to help adjust the HF compensation of a probe.

For an interesting exercise, experiment with the output of a function generator doing pulses (or pulse generator, of course) and then adjust and misadjust the HF compensation on the probe.  I found interesting results.  The PRF of the pulse and the duration are significant.

Harvey

On 8/3/2020 2:21 PM, Colin Herbert via groups.io wrote:
There is a bit of a clue in that the calibration loop on the right-hand side is marked with an arrow pointing left and the words "5mA" followed by a square-wave. The calibration BNC on the front panel is marked "1 kHz". This should lead one to think that the BNC on the front-panel is for Time/Div calibration and the loop on the right side is for Current/Div calibration. I will have to look at how the "1kHz" is generated to see if it really is accurate (most of these are not that accurate).
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Richard P via groups.io
Sent: 03 August 2020 19:02
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to understand the 453 calibrator

Harvey (and all),

Yeah, my loop is directly grounded, so I will get my calibration voltage signal from the BNC on the front panel. Works fine.

Glad to learn aboutthis. Thanks, all.

R






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